1. (战争中的)前线，前方
    The front line is the place where two opposing armies are facing each other and where fighting is going on.

    e.g. ...a massive concentration of soldiers on the front line.
           在前线大规模的兵力集结

2. (国家)位于战争(或冲突)前线的，与敌对国毗邻的
    A front line state shares a border with a country that it is at war with or is in conflict with.

    e.g. ...the front-line states bordering South Africa.
           和南非接壤的前线国家

3. 处于第一线;居于极重要岗位
    Someone who is in the front line has to play a very important part in defending or achieving something.

    e.g. Information officers are in the front line of putting across government policies.
           新闻发言官处于传达政府政策的第一线。

1. the line along which opposing armies face each other

    Synonym: battlefrontfront